To check that a piece of electronic equipment is working properly, it is usual to provide for the incorporation of built-in tests when designing it. These tests are of two types:
off-line tests which take place at least when the equipment is started up, and achieve a fairly complete and precis verification of its state before its effective operational starting; during these tests, the basic function fulfilled by the piece of equipment is not performed.
on-line tests which occur permanently during the operational functioning of the equipment and which should, therefore, be transparent with respect to this functioning, i.e. should not disturb it; they are often less complete than the former tests but they are nonetheless capable of detecting and approximately localizing a failure that takes place during operation.
The present invention concerns an on-line testing method applied to a radar information display device, notably to an image digital converter.
One of the common methods applied for on-line tests is input/output comparison. The equipment is divided here into some essential functions at the level of which the comparisons are made between the input signals and output signals of the function considered. It is then a question of ascertaining that, for a given set of input values of the function, the output result is actually the expected result, this result being obtained by computation, elsewhere, using software for example, of the result that has to be obtained by applying the function to the same set of values.
For the implementing of this method, two methods are known:
the input data of the function to be tested are useful data, which go through the whole processing chain of the equipment; these pieces of data are then recorded at input and output of the function being tested; in deferred time, the function considered is subjected to input recording to obtain the theoretical output values which are compared with the recording of the real output signals, and the result of the comparison then gives the indication of proper functioning or of malfunctioning;
the input data of the function to be tested may be interrupted, either because they are known beforehand or because they are temporarily insignificant; a test sequence is then introduced at input of the considered function; at output of this function, the pieces of data corresponding to this sequence are, on the one hand, recorded and, on the other hand, blacked out so that they are not transmitted to the rest of the processing chain; the function under test is furthermore subjected to the input sequence and, as previously, a verification is done, as above, of the real output sequence recorded.
The advantage of the second method lies in the possibility of choosing the test sequence, which may then be adapted more particularly to the function to be tested, and hence it lies in greater efficiency. Its drawback is that it is necessary to have a free zone available, where the pieces of data are not significant or have a particular known value, which may be restored at a point further downline of the processing chain.
In the case of a display of radar information obtained by successive scans of a zone, for example by the rotation of an antenna, according to the invention during a given antenna rotation, there is determined a zone where there is no radar echo; knowing the speed of the objects displayed (aircraft for example), a second zone is determined, located within the first one, where there will certainly be no echo during the next antenna rotation, and the operation is done substantially according to the above-described second method, in inserting and then blacking out test sequences.
More precisely, the method according to the invention is a method for the on-line testing of a device for the display of pieces of radar information, these pieces of information being obtained by successive scans of a predefined zone; the device has a processing chain wherein a first determined function, at least, is performed; the method principally comprises the following stems:
analysis of the incident radar information corresponding to a first scan to determine a first zone (Z.sub.0) the video signal of which is substantially zero;
determination of a second zone (Z.sub.1), located inside the first zone, wherein the video signal will be substantially zero at the following scan, called the second scan;
emission, during the second scan and instead of the incident radar information corresponding to the second zone, of a series of signals forming a test sequence;
execution of the first function on the test sequence;
memorizing of the test sequence at output of the first function;
comparison of the memorized sequence with its theoretical value and emission of a piece of information of error in case of difference;
blacking out of the test sequence at output of the first function, with respect to the sequence of the processing chain.
Other objects, particular features and results of the invention will emerge from the following description, illustrated by the appended drawings, which represent: